Medical Screening: Helpful or Harmful?

by Caroline Crocker with input from an anonymous medical professional.

Words every man or woman does not like to hear from his or her physician, “It looks like it is time for your prostate screening or mammogram.” There is no doubt that  screening procedures are unpleasant, but is it possible that they do more harm than good? And is there a viable alternative?

Let’s consider mammograms. According to an article by Devra Davis, PhD, the first study on using X-rays to detect breast cancer was conducted in 1963; it was found that mammograms are useful in prevention of breast cancer deaths in women over 50. Soon afterwards (1972), the National Cancer Institute and the American Cancer Society launched a national program aimed at encouraging all women to have screening mammograms. It is troublesome that no studies on the benefit of mammograms in younger women had been conducted. Equally of concern, there were no national mammography standards until 1994; the equipment was often substandard and even receptionists could administer the X-rays.

But, it is well-known that X-rays cause DNA damage, not to mention damage to the cellular repair enzymes–and that this can then lead to mutations during subsequent cell division, which can lead to cancer. This is why the technician leaves the room. The problem in mammograms is exacerbated by the mechanical trauma inflicted during the procedure (many women come away with bruised breasts), which necessitates the body repairing damaged areas by initiating cell division and activating immune system cells. The result is a combination of damaged DNA and cells that are trying to divide–a recipe for cancer.

Therefore, an analysis of the alleged benefit derived from mammograms must take into account the increased risk of cancer that an annual procedure brings. It is generally accepted that mammograms enable a 20% average increase in detected cancer (and a 30% decrease in death rate), but this is debatable in younger women where it is difficult to distinguish cancerous tissue from dense healthy tissue and radiation exposure carries more risk.  A recent study suggests that 86/100,000 of women receiving an annual mammogram after the age of 40 will get radiation-induced cancer.

More specific information can be obtained from work coming out of Oxford. Here and elsewhere it was shown that annual mammograms before the age of 40 cause about 5x more cancer deaths than they prevent and mammograms between the ages of 40 and 50 cause as many cancer deaths as they prevent. After the age of 50, the breast tissue decreases in density, the cell division rate slows down, and the number of age-related mutations increase, so that mammograms become an effective means of reducing breast cancer mortality in post-menopausal women. That is, on average, mammography prevents more deaths than it causes in older women.

Of course, more research is required–it appears that even debates about the optimum radiation dosage have not been settled. The assumed mutation rate caused by mammograms is based on high energy X-rays. But, recent data suggests that the low energy X-rays used in mammograms cause 4.4 times as much damage as the high. In other words, the published risks of having an annual mammogram may be more than quadruple what we thought they were. And this is only the mutation risk.

Those of us who have been told that their mammogram was abnormal when there was no cancer, or normal when there is, will be aware than there are other risks, as well: false positives and false negatives. A false positive occurs in about 10% of women. This results in obvious stress, but also in additional procedures like follow-up X-rays (I had ten on each breast), which increase the radiation dosage. If results from these are unclear, the patient undergoes ultrasound, which picks up about 1% of cancers not detected by mammogram, and MRI, which detects only 0.3% more. Both of these procedures also have high false positive rates. So, eventually, the patient may need to undergo a surgical procedure like a biopsy or lumpectomy, even though they will eventually be found not to have cancer.

Then, there are the false negatives. Mammograms only detect just over half of the cancers in high risk women–leaving women thinking they do not have breast cancer when in fact they may. This is a problem because breast cancer is on the rise. Interestingly, according to a series of letters in the Lancet 346(8972):436-9, ductal carcinoma in situ (DCIS) has increased by 328% since the advent of mammograms. 200% of this increase in DCIS is said to be directly caused by them. Now, many ductal carcinomas resolve on their own or are nonmalignant, but who wants to take the risk? The result is that many women who should not be treated are, often aggressively, and some women who should be treated do not find out until the cancer has progressed.

What is the answer? It is not obvious. Certainly, the data suggests that women under 50 should not have mammograms. And, if you have an abnormal mammogram, perhaps follow up should be accomplished by ultrasound and/or MRI, not more radiation. But, what about all the other cancer screening tests: P.S.A blood tests, colonoscopies, etc? The verdict for those that have been evaluated differs according to the test. For many of the screening tests, studies to determine if they do more harm than good have not been accomplished. So, as always, the onus falls on us. Don’t just believe what you are told–do some investigation, think about it, and decide for yourself. A good place to start might be the article by two physicians that triggered AITSE’s investigation into this issue.